Apparatus for operating vibratory motors



June 30, 1942.

H. H. HITTSON APPARATUS FOR OPERATING VIBRATORY MOTORS Filed Jan. 10,1941 41070? GENE/FAME M0703 GEM/[19703 lbs 151:9?

/NVEN7'OR HARKER H. HITTSON, BY 44 724M,

Ari-9.

Patented June 30, 1942 2,287,880 APIAARATUS FOR. OPERATING VIBRATORYMOTO Harker H. Hittson, Columbus, Ohio, assignor to The JeffreyManufacturing Company, a corporation of Ohio Application January 10,1941, Serial No. 373,985

Claims.

This invention relates to. a method of and apparatus for operating andcontrolling vibratory motors, and more specifically vibratory motorconveyors, so as to maintain the amplitude of vibration of the vibratorymotor or conveyor deck substantially constant at a pre-selected valuewhich may be varied over a wide range.

An object of the invention is to provide a new and improved method andapparatus of the above mentioned type in which the amplitude control isautomatic and continuous and is effected by adjusting the frequency ofthe current delivered to a vibratory electro-magnetic motor toward orfrom its natural period of vibration so that said amplitude of vibrationis maintained substantially constant within a narrow range at apreselected value which may be varied under the control of the operator.

Another object of the invention is to provide apparatus of the abovementioned type in which the control circuit is simplified frompreviously known control circuits and in which the frequency of thecurrent delivered to the vibratory motor is controlled independently ofthe natural period of vibration of the vibratory motor, but which bearsa variable relation to said natural period of vibration to effect thedesired amplitude control.

Other objects of the invention will appear hereinafter, the novelfeatures and combinations being' set forth in the appended claims.

In the accompanying drawing:

Fig.1 shows a preferred embodiment of the system of my invention;

Fig. 2 shows a modification of a portion of the system of Fig. 1; and

Fig. 3 shows another modification of a portion of the system of Fig. 1.

It may be pointed out that many of the details of the control systemherein disclosed are identical with the system illustrated particularlyin Fig. 4 of the application of Clyde W. Baird, Serial No. 371,314 for aVibration control apparatus, filed December 23, 1940, but certainfundamental differences have been made in the system of said Bairdapplication which make for an entirely different overall mode ofoperation.

Referring particularly to Fig. 1 of the drawing, the system of myinvention includes a pair of power mains I and In! which are fed fromany desired source of alternating current and provided with a magneticswitch 2 having a start push button 3 which is normally open, and a stoppush button 4 which is normally closed.

When the switch 2 is closed, as hereinafter described, after apredetermined time interval following the energization of a circuit forheating the filaments of the gaseous discharge tubes, in response to theoperation of push button 3, a transformer 1 is energized, thesecondaryterminals of which areconnected to the plates of gas-filledelectronic discharge tubes 8 and 9 which act as a full-wave rectifier torectify the alternating current delivered thereto, which rectifiedcurrent is delivered over conductors I0 and H to a vibratory motor I2preferably forming a vibratory conveyor such as disclosed in the patentto James A. Flint, No. 2,094,787, dated October 5, 1937, there being anammeter provided in conductor to as illustrated at I3.

To start the operation of the system a switch I4 is closed whichenergizes a transformer I5 which has three secondary windings, therighthand one of which energizes the filaments and cathodes of theelectronic discharge tubes 8 and 9, .the left-hand one of whichenergizes the filaments of electronic discharge tubes 49 and 50 and alsosupplies the voltage for a full-wave rectifier bridge 8| which providesa direct current negative bias on the grids of the tubes 49 and 50, allover obvious circuits. The more complete circuits for the tubes 49 and50 and the bridge 8| are described hereinafter. The third of saidsecondary windings of transformer l5 energizes the heater filaments ofelectronic tubes'3l and 83 in series, thus insuring that either both orneither of said tubes will be energized at the same time.

The closing of the switch [4 starts into operation a filament heatingtime delay circuit I! which is similar to that described in completedetail in the above-identified application of Clyde W. Baird, which isoperative so that after a predetermined time interval its relay I8 isenergized and in addition to closing a holding circuit on itself,connects conductors l9 and 20 by way of normally open contacts 2| whichmakes voltage available for the magnetic switch 2 since conductor I9 isconnected to main I through switch [4, and conductor Ml extends to saidswitch 2. A signal lamp 22 connected through a resistor to conductor I9!and also connected to conductor 20, is energized upon the closing ofcontacts 2|,

thus signaling the operator that he may close the contacts of switch 2by pushing the button 3. This time delay relay I1 is provided to insureadequate heating of the cathodes of gaseous discharge tubes 9 and 9before voltage is applied to the anode or plate circuits thereof toprevent damage to said tubes. When relay 2 is closed, power is suppliedto tubes 9 and 9 and this closed conditionis indicated by signal lamp I6being energized through the third set of terminals of said switch andthrough contacts 2I.

The method oi? automatically controlling the amplitude of vibration ofthe vibratory motor I2 to maintain it substantially constant within aDre-selected but adjustable range, as determined by the operator, isfundamentally different from the method disclosed in the aboveidentified application of Clyde W. Baird and from other known priordevices. The frequency of the impulses or undulations of the currentwhich flows to the motor I2 is not necessarily or even probably the sameas the natural period of vibration of said motor I2, but the naturalperiod of v1- bration of the motor I2 is an important factor and thefrequency of the current delivered to said motor I2 is regulatedautomatically so as to move toward or from said natural period ofvibration in response to amplitude variations from a pre-selected value.In this connection it is a known characteristic of a vibratoryelectromagnetic motor that if the current delivered to it issubstantially constant, its amplitude may be adjusted by adjusting thefrequency of the current toward and from said natural period ofvibration either above it or below it. The maximum amplitude will berealized when the delivered frequency coincides with .the natural periodof vibration and if the delivered frequency moves either above or belowthe natural period, the amplitude of vibration will progressivelydecrease with the departure therefrom.

I make use of this phenomena by delivered current to said motor I2 at afrequency which is to be controlled and varied automatically in responseto amplitude variations from a preselected value so as to bring thedelivered frequency closer to the natural period of vibration. of themotor I2 in case the correction requires an increase in the amplitude ofvibration,and-

conversely if an opposite correctionis required.

There is another important distinction 'betweenmy system. and that ofthe Baird application above mentioned, in that there is no difllcultyfrom thejsource 4II-so that there is no current flow in "resistors 48and'44, but durirmunstable conditions=-or when the-amplitude of vibrationor alternating current because an alternating;

current generator of one kind or another is provided and this insuresalternating or undulating current of-approximately the requiredstartinfrequency, and control is effected by adjusting this frequency whenevernecessary.

. 'It is evident that the current which flows through the tubes 8 and 8would be direct ourrent in the absence of some modifying means,

and this modifying means which is eilective to convert it into impulsesor undulating current at a controllable frequency, includes the grids ofsaid tubes 8 and 8 which are connected together .8 connected thereto.

and to a conductor 25, said grids having a filter A I shall now describethe pickup and automatic v control circuit which, as above stated,follows in many details the disclosure of the application;

' of Clyde W. Baird, above identified, and particularly thesystem shownin Fig. 4 of .the drawing mum amplitude control resistor 32, andamplitude control resistor 34 having a variable tap 35. The operator byadjusting tap 35 variably preselects the operating amplitude ofvibration within the limits provided by the maximum, the

minimum of which may be controlled by resistor 38 and its variable tap.The adjustable voltage as determined by the position of the variable tap35 is transferred to transformer 38 having in its output circuit a fullwave rectifier vacuum tube 31 which rectifies the current, deliveredthereto which flows through balancing bridge resistor 38 provided with alay-pass filter condenser 39. Resistor 38 is'one' branch of a bridge,the other branch of which includes a source of constant direct currentvoltage indicated generally by the reference character 48. Said sourceof constant direct current voltage is provided by a transformer 82 whichderives power from the mains I and IM over an obvious circuit whenswitch I4 is closed. Connected to the secondary of the transformer 82 isa full wave rectifier including, a vacuum tube 83, the output circuit ofwhich extends from the cathode to the center tap of the secondary of thetransformer 82 and includes a bridge or network 84 comprising acondensor 85 having a resistor 88 connected across the terminals thereofand across which terminals there is connected a neon tube 81 and aresistor 88, that is, neon tube 81 and resistor 88 are effectivelyconnected in series and together are in parallel withresistor 88 andcondensor 85.

In such a network the voltage drop across the terminals of the neon tube81 will be substantially. constant regardless of any variations in linevoltage, and thisconstant voltage'dropis connected in the bridgeworkincluding resistors 38 and-tworesistors 43 and which are connectedacrossconductors 4I and 42.fi In other words, a bridgework is formedbyresistors 38, 43 and 44- and the constant direct current. voltagesource 48, and during stable conditions the voltage drop across resistor38 will match the constant voltage of the motor. I2 increases ordecreases rfrom its preselected'--value; there will be 'a current: flowthroughres'istors 43 and44 in opposite directions where 'oppositeconditions prevail, to effect automatic. control as hereinafterdescribed.

The-center tap of the two resistors 43 and 44 is -connected-to thenegative terminal of the full wave'rectifier 8| which provides a normalnegative bias on the two gaseous discharge tubes 48 and 58 ashereinafter described. Filtering condensors 41 and 48 are connectedacross resistors 43 and 44, respectively, through the full waverectifier 8|.

The control grids of the gaseous tubes 48 and 5 are connected through.protecting resistors to conductors 42 and M, respectively, and the inputcircuits to said tubes are connected to the cathodes thereof from thecenter tap of the condensors 41 and 48 through a network formed byccndensor 55 and adjustable resistor 58 to provide an anti-huntingcircuit for the motor 24 hereinafter described more completely.

Tubes 49 and 58 have stabilizing or. protecting grids which areconnected in parallel with the cathodes. The negative bias provided bythe full wave rectifier bridge BI is sufllcient to bias the tubes 48 and58 normally to cut off, and these tubes will only fire in response to anunbalanced condition. For example, if the amplitude of vibration of themotor I2 exceeds a preselected value, the voltage drop across resistor30 will exceed the fixed voltage derived from source 40,

and current will flow through resistors 43 and 44 in that sequence. Thevoltage drop across resister 43 will oppose the negative bias on bridgeso that the grid of tube 49 becomes less negative and this tube willfire. The voltage drop across resistor 44 will simultaneously increasethe negative grid bias on tube 50 which is without consequence.Conversely, if the amplitude of vibration of the motor I2 falls belowthe preselected value, the voltage drop across resistor 30 will fallbelow the voltage of the constant source 40, and current will flowthrough resistors 43 and 44 in that sequence, in which case the voltagedrop across resistor 44 will reduce the negative bias on the grid oftube 50, causing it to fire, while the voltage drop across resistor 43increases the negative bias on the grid of tube 49, which is withoutconsequence.

The above-described anti-hunting network was described as in the inputcircuits of tubes 49 and 50, but it is also in the output circuitsthereof since it leads to the cathodes of said tubes, and said outputcircuits extend from said cathodes through said anti-hunting circuit byway of common conductor 54 to a common terminal of a pair of primarywindings of separate transformers 52 and 53, the other terminals ofwhich are connected to the anodesor plates 49 and 50, respectively.

The secondaries of transformers 52 and 53 are connected across a pair ofshading coils 51 and 58, respectively, of the motor 24, which motor 24adjusts the variable tap I 02 of a motor driven rheostat I03, ashereinafter described more comconductors 59, 60 and GI. .The motor 24 isof well known construction and when shading coil 51 is short-circuitedit will rotate in one direction, and when shading coil 58 isshort-circuited it will rotate in the opposite direction, and whenneither is short-circuited, it will not move. These coils 'I,an d 58 arenormally energized because the miotor 24 has a field coil 62 which isconstantly I energized whenever switch 2 is closed since it is connecteddirectlyacross conductors I and IOI.

I By virtue of the magnetic coupling between the coil 52 and the shadingcoils 51 and 59, voltage is normally induced in each of said shadingcoils I and this voltage is delivered to the secondary windingsof thetransformers 52 and 53 by way of conductors 59, 60 and GI, this voltagebeing the r' vplatevoltage for the two tubes 49 and 50 after it isstepped up by transformers 52 and 53. As a result-whenever tube 49becomes conducting as above described, it effectively short-circuitstransformer 52 which effectively short-circuits shading coil 58 therebycausing a corrective adjustment of the variable tap I02. Similarly, whentube 50 becomes conducting transformer 53 is effectively short-circuitedand shading coil 51 is short-circuited causing a reverse correctiveoperation of tions. The frequency of the current delivered to said motorI2 is determined by a small motor 1 generator set A which is preferablya direct current motor driving an alternating current gen- I This motorgenerator set A is very small control the grids of the tubes 0 and 9,the output pletely, the connection between said transformer .secondariesand shading coils being by way of 1 thereof extending to said grids byway of conductors 25 and I04, conductor I04 leading to the cathodes ofsaid tubes 8 and 9 through a protective resistor, and conductor 25leading to .the grids through the filter 26 as above mentioned.

It is of course evident that the frequency of the current on theconductors 25 and I04 will control the frequency of the currentdelivered to the motor I2 over conductors l0 and II. Also the frequencyof the generator of the motor generator set A or in other words thefrequency on the conductors 25 and I04, may be adjusted by adjusting thespeed of the driving motor of said motor generator set and this isadjusted automatically by adjusting the variable tap I02.

In addition to the rheostat I03 I preferably also provide a rheostat I05which is manually adjustable and which is preferably so adjusted that incase the frequency variations are below the natural period of vibrationof the motor I2, it would be impossible even though all of rheostat I03is cut out, to generate a frequency by motor generatorset A, which is inexcess of the natural period of vibration of the motor I2.

From the above description it is obvious that in the operation of thissystem the adjustable contact 35 may be moved to any desired position bythe operator to give a preselected normal amplitude of vibration of themotor I2. This is preferably effective with the pointer I02substantially midway of its two extreme positions on the rheostat I03.Under these conditions the frequency of the motor generator set A issuch that if it is increased the amplitude of vibration of the motor I2will increase, and if it is decreased said amplitude of vibration willdecrease. This assumes that the operation of the motor I2 is at afrequency below the natural period of vibration, but of course thecontrol may be operated always above the natural period of vibration byobvious adjustments. If the amplitude of vibration thereafter increases,the pointer I02 will be automatically adjusted to decrease the frequencyof the motor generator set and thus automatically decrease the amplitudeof vibration until it returns to its preselected value. A reversecondit-ion will produce a reverse result and thus the amplitude ofvibration will always be maintained constant.

The apparatus above described from the pick up device 2! through themotor 24 constitutes means for constantly and automatically measuringthe amplitude of vibration of the motor I2 by comparing it with apreselecteddesired value.

If pointer I02 is stationary said motor amplitude coincides with saidpreselected value. If it moves to the left or the right the amplitude istoo low or too high, as the case may be.

In Fig. 2 I have shown a modfication of the preferred embodiment of myinvention in which the motor generator set A is made of much greatercapacity than that previously described so that its output is feddirectly to the motor I2 by way of -conductors I0 and II. In otherwords, this eliminates the tubes 9 and 9 and their various controls aswell as the transformers I. This will also involve certain obviouschanges in the connections to the switch 2.

In Fig. 3 of the drawing I have illustrated another modification of thepreferred system of Fig. 1, in which a non-rotary type of generator issubstituted for the .rotarygenerator A,'said non-rotary generator beingillustrated at B. This generator B may be of any well known design suchas low frequency electronic tube oscillater or a relaxation oscillatorof known design.

The frequency variations in this system are obtained by adjusting thevalue of some impedance, such as an adjustable condenser, reactor orresistor, this adjustment ofcourse being effected automatically by themotor 24.

Obviously those skilled in the art may make various changes in thedetails and arrangement of parts without departing from the spirit andscope of the invention as defined by the claims hereto appended, and Itherefore wish not to be restricted tothe precise construction hereindisclosed.

Having thus described and shown an embodiment of my invention, what Idesire to secure by Letters Patent of'the United States is:

1. In combination, a vibratory electro-magnetic' motor which has anatural period of vibration, means for delivering current impulses ofvariable frequency to said motor including electronic valve means, meansfor constantly and automatically measuring the amplitude of vibration ofsaid motor, means controlling said valve means including a variablefrequency source to determine the frequency of the current impulsesdelivered to said motor, said measuring means being connected to varythe frequency of said variable frequency source in response to measuredchanges injthe amplitude of vibration of said motor, all whereby saidamplitude of vibration of said motor is maintained substantiallyconstant.

2. Vibration control apparatus comprising the combination with avibratory electro-magnetic motor having a natural period of vibration,of m ms for supplying variable frequency current to said vibratory motorincluding electronic tube means capable of producing direct current andhaving control grid means, a motor generator set having a variable speedmotor and connected to control said grid means thereby to control thefrequency of the current delivered by said electronic tube means to saidmotor, means constructed and arranged to respond differently to reversevariations inthe amplitude of vibration of said vibratory motor from apreselected motor of said motor generator set upwardly or downwardlyselectively, thereby to adjust the frequency of the current delivered tosaid vibratory motor toward or from its naturalv period I vibration andthereby to maintain the amplitude motor having a natural period ofvibration, of

means for supplying variable frequency current to said vibratory motorincluding electronic tube means having control grid means and a variablefrequency generator connected to said grid means to control thefrequency of the current delivered to said motor, means constructed andarranged to respond differently to reverse variations in the amplitudeof vibration of said vibratory motor from a preselected value, and meansoperable by different responses of said response means to adjust thefrequency of the variable frequency generator selectively upwardly ordownwardly thereby to adjust the frequency of the current delivered tosaid vibratory motor toward or from its natural period of vibration andthereby. to maintain the amplitude of vibration ofsaid vibratory motorsubstantially constant.

4. Vibration control apparatus comprising the combination with avibratory electro-magnetic motor having a natural period of vibration,of means for supplying variable frequency current to said vibratorymotor including electronic tube means having control grid means and avariable frequency electron discharge generator, means connecting saidgenerator to said control grid means, means constructed and arranged torespond. differently to reverse variations in the amplitude of vibrationof said vibratory motor from a preselected value, and means operable bydifierent responses of said response means to adjust the frequency ofthe variable frequency generator selectively upwardly or downwardlythereby to adjust the frequency of the current delivered to saidvibratory motor toward or from its natural period of vibration andthereby to maintain the amplitude of vibration of said vibratory motorsubstantially constant.

5. Vibration control apparatus comprising the combination with avibratory electro-magnetic motor having a natural period of vibration,or means for supplying variable frequency current to said vibratorymotor including an oscillating generator, and means constructed andarranged to respond to variations in the amplitude of vibration of saidvibratory motor from a preselected value, and means controlled by saidlast named means to adjust the frequency of the current delivered tosaid vibratory motortoward or from its natural period of vibrationthereby to maintain the amplitude of vibration of said vibratory motorsubstantially constant.

HA-RKER H. HITISON.

